Light output system with reflector and lens for highly spatially uniform light output

ABSTRACT

In some embodiments, optical systems with a reflector and a lens proximate a light output opening of the reflector provide light output with high spatial uniformity and high efficiency. The reflectors are shaped to provide substantially angularly uniform light output and the lens is configured to transform this angularly uniform light output into spatially uniform light output. The light output may be directed into a spatial light modulator, which modulates the light to project an image.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/856,829, filed Jul. 1, 2022, entitled “LIGHT OUTPUT SYSTEM WITHREFLECTOR AND LENS FOR HIGHLY SPATIALLY UNIFORM LIGHT OUTPUT”, which isa continuation of U.S. patent application Ser. No. 16/378,409, filedApr. 8, 2019, entitled “LIGHT OUTPUT SYSTEM WITH REFLECTOR AND LENS FORHIGHLY SPATIALLY UNIFORM LIGHT OUTPUT”, which is a continuation of U.S.patent application Ser. No. 15/442,451, filed Feb. 24, 2017, entitled“LIGHT OUTPUT SYSTEM WITH REFLECTOR AND LENS FOR HIGHLY SPATIALLYUNIFORM LIGHT OUTPUT” (now U.S. patent Ser. No. 10/306,213), whichclaims the benefit of priority under 35 U.S.C. § 119(e) of U.S.Provisional Application No. 62/300,742, filed Feb. 26, 2016, entitled“LIGHT OUTPUT SYSTEM WITH REFLECTOR AND LENS FOR HIGHLY SPATIALLYUNIFORM LIGHT OUTPUT”. The disclosures of these priority applicationsare hereby incorporated by reference in their entireties.

This application also incorporates by reference the entirety of each ofthe following patent applications: U.S. application Ser. No. 14/555,585filed on Nov. 27, 2014; U.S. application Ser. No. 14/690,401 filed onApr. 18, 2015; U.S. application Ser. No. 14/212,961 filed on Mar. 14,2014; and U.S. application Ser. No. 14/331,218 filed on Jul. 14, 2014.

BACKGROUND Field

The present disclosure relates to light output systems and, moreparticularly, to light output systems having reflectors and lens. Insome embodiments, the light output systems may be part of augmented andvirtual reality imaging and visualization systems.

Description of the Related Art

Imaging and visualization systems may utilize systems that output lightinto a light modulating device that then modulates and projects thelight to form images in the eyes of a viewer. There is a continuing needto develop light projection systems that can meet the needs of modernimaging and visualization systems.

SUMMARY

In some embodiments, an optical system is provided. The optical systemcomprises a reflector, which comprises a light input opening, a lightoutput opening, and reflective interior sidewalls extending between thelight input opening and the light output opening. The optical systemalso comprises lens proximate a light output opening of the reflector.The sidewalls of the reflector may be shaped to provide substantiallyangularly uniform light output, and the lens may be configured toconvert the substantially angularly uniform light output tosubstantially spatially uniform light output. In some embodiments, thereflector is one of an array of reflectors, each reflector having anassociated lens forward of the output opening of the reflector.

The optical system may further comprise a light modulating deviceconfigured to receive light outputted by the reflector through the lens.The optical system may also further comprise a stack of waveguides, eachwaveguide comprising a light incoupling optical element configured toreceive light from the light modulating device. The light incouplingoptical element of each waveguide may be spatially offset from the lightincoupling optical element of other waveguides, as seen along the axisof propagation of the light into the stack. The spatial arrangement ofthe reflectors, as seen in a plan view, may correspond and alignone-to-one with a spatial arrangement of the light incoupling opticalelements.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a user's view of augmented reality (AR) through an ARdevice.

FIG. 2 illustrates an example of wearable display system.

FIG. 3 illustrates a conventional display system for simulatingthree-dimensional imagery for a user.

FIG. 4 illustrates aspects of an approach for simulatingthree-dimensional imagery using multiple depth planes.

FIGS. 5A-5C illustrate relationships between radius of curvature andfocal radius.

FIG. 6 illustrates an example of a waveguide stack for outputting imageinformation to a user.

FIG. 7 illustrates an example of exit beams outputted by a waveguide.

FIG. 8 illustrates an example of a stacked waveguide assembly in whicheach depth plane includes images formed using multiple differentcomponent colors.

FIG. 9A illustrates a cross-sectional side view of an example of a setof stacked waveguides that each includes an incoupling optical element.

FIG. 9B illustrates a perspective view of an example of the plurality ofstacked waveguides of FIG. 9A.

FIG. 9C illustrates a top-down plan view of an example of the pluralityof stacked waveguides of FIGS. 9A and 9B.

FIG. 10 illustrates an example of a reflector having the profile of acompound parabolic concentrator (CPC).

FIG. 11 illustrates an example of an optical system having a reflectorand a lens.

FIG. 12 illustrates an example of an optical system having a lightemitter, a reflector, and a lens.

FIG. 13 illustrates an example of the light output from the opticalsystem of FIGS. 11-12 .

FIGS. 14A-14F illustrate examples of reflectors having light inputopenings and light output openings with different shapes.

FIGS. 15A and 15B illustrate examples of uniformity maps for the lightoutput of the reflectors of FIGS. 14A-14C and 14D-14F, respectively.

FIG. 16 illustrates an example of a map showing the intensity of lightoutput, in angle space, for the reflector of FIGS. 14A-14C inconjunction with a lens.

FIGS. 17A-17B illustrate perspective views of examples of arrays of thereflectors of FIGS. 14A-14C and 14D-14F, respectively.

FIG. 18 illustrates a perspective view of an example of an opticalsystem having arrays of light emitters, reflectors, and lens, and amask.

FIG. 19 illustrates a perspective view of an example of body of materialhaving an array of reflectors and indentations for light emitterstructures such as wiring.

FIGS. 20A-20 b illustrate perspective views of examples of a body ofmaterial having reflectors with different heights.

FIGS. 21A-21E illustrates various views of an example of a reflector.

FIGS. 22A-22B illustrate additional perspective views of the reflectorof FIG. 21 .

FIGS. 22C-22D illustrate perspective views of the reflector of FIG. 21as seen from the light output opening side and the light input openingside, respectively, of the reflector.

FIGS. 23A and 23B illustrate examples of uniformity maps for the lightoutput of the reflectors of having rounded profiles and having sharpcorners at the intersections of interior sidewalls, respectively.

The drawings are provided to illustrate example embodiments and are notintended to limit the scope of the disclosure.

DETAILED DESCRIPTION

Display systems may form images by modulating light from a light emitterand then projecting that light for viewing by a viewer. Some imagingsystems may utilize arrays of light emitters, each of whichindependently provide light to a light modulator. The light emitterspresent various challenges. For example, systems with arrays of lightemitters may be complex, with multiple structures utilized to direct thepropagation of light to the light modulator. Due to the complexity ofthe assembly, the systems may be difficult to manufacture.

In addition, it will be appreciated that the brightness uniformity ofthe images formed by the display system may be dependent upon thespatial uniformity of the light received by a light modulator from thelight emitters. As a result, to display images with good brightnessuniformity, it is desirable for the light received by the lightmodulator to be spatially uniform.

Advantageously, according to some embodiments, optical systems with areflector and a lens proximate a light output opening of the reflectorprovide light output with high spatial uniformity and high efficiency.Preferably, the reflectors are shaped to provide substantially angularlyuniform light output and the lens is configured to transform thisangularly uniform light output into spatially uniform light output. Thereflector has a light input opening for accommodating and/or receivinglight from a light emitter and a light output opening for outputtingthat received light. In some embodiments, the light emitter emits lightwith a lambertian angular distribution. In some embodiments, the lightemitter is an extended light source and may be, e.g., a light emittingdiode. In some embodiments, the shapes of the light input and outputopenings may be different. In some embodiments, the lens is proximate(e.g., forward of) the light output opening of the reflector.

In some embodiments, the curvature of the interior reflective surfacesof the reflector, as seen in a cross-sectional side view, may follow thecontours of an ellipse, hyperbola, or biconic shape. In someembodiments, the interior reflective surfaces of the reflector may havea generally linear profile as the reflector tapers from a relativelylarge light output opening to a smaller light input opening. Preferably,the reflective surface of the reflector is shaped to substantiallycollimate a set of edge rays corresponding to a design shape orsub-aperture fixed in the emitter surface. It will be appreciated thatmore than one set of edge rays may be included in the design of thereflector. For instance, a reflector designed to allow +/−50 microns ofaxial light emitter shift may be designed with several sets of edge raysthat span this range, with the reflector shape chosen to substantiallycollimate each set. In some embodiments, the resulting shape of thereflective surface of the reflector may deviate slightly from anidealized off-axis parabolic section but is may be substantially similarto the shape of a compound parabolic concentrator (CPC). It will beappreciated that the shape and parameters for the lens and light emittermay be jointly chosen to achieve desired levels of spatially uniformlight output and efficiency.

In some embodiments, the reflective interior surface of the reflectorhas the profile (as seem in a cross-sectional side view) of a compoundparabolic concentrator (CPC), with this profile or curvature beingpresent at least in cross-sections taken along two midplanes extendingalong the height axis of the reflector, with the midplanes beingorthogonal to one another. It will be appreciated that the height of thereflector is the distance between the light input opening and the lightoutput opening.

In some preferred embodiments, the interior surface of the reflector mayhave multiple sides and all of those sides may have a CPC profile, asseen in a side view. In addition, as seen in cross-sectional side viewstaken along planes transverse to the height axis of the reflector, allinterior sidewalls may be linear or flat. Thus, the interior sidewallsmay be considered to be facets and form corners at the intersections ofthese interior sidewalls. Preferably, these corners at intersections ofthe interior sidewalls are sharp corners due to the linear nature of thesidewalls, as noted above. In some embodiments, two opposing interiorsidewalls may have a different CPC profile from other interiorsidewalls. In some embodiments, all of those other interior sidewalls ofthe same CPC profile. In some other embodiments, at least two interiorsidewalls, or all the interior sidewalls, are substantially linearextending from a light input end to a light output end of the reflector.Preferably, the total number of interior sidewalls is 6 or more, or,more preferably, 8 or more.

In some embodiments, a plurality of the reflectors and associated lensesform an array that provides discrete, spatially-separated sources oflight output to, e.g., a light modulator. For example, a different lightemitter may output light into each reflector and associated lens. Insome embodiments, a mask may be provided forward of the lens, to providelight output with a desired crossectional shape. In some embodiments, atleast some of the light emitters may emit light of different wavelengthsthan others of the light emitters. In some embodiments, at least some ofthe reflectors may have different heights than others of the reflectors.In some embodiments, the reflectors, lenses, and/or the mask may beformed in separate plates of material, which may later be assembled intoa light output module.

It will be appreciated that CPC's are conventionally used to collectlight, e.g., in solar energy collectors, or to output light inspotlighting applications. CPC's output light with good angularuniformity, but the light may form circular shapes with low lightintensity at the interiors of the circular shapes, particularly wherethe CPC has a circular shape at its output opening. Such circular shapesare indicative of unacceptably spatially non-uniform light output, whichhas prevented the use of CPC's for providing light in imaging systems.

It has been found, however, that highly spatially uniform light outputmay be provided using a reflector having a profile that providesangularly uniform light output in conjunction with a lens. In someembodiments, the lens takes advantage of the highly angularly uniformlight output of the reflector and performs a Fourier transform on thislight, such that the light is converted into highly spatially uniformlight after passing through the lens.

Advantageously, the high spatial uniformity allows the light outputsystem to be utilized in various optical systems in which highlyspatially uniform light output is desired. For example, the opticalsystem may be a display system and the light output system may outputlight into a light modulating device for forming images. The lightoutput system may also provide high efficiency, which can increase imagebrightness. For example, the shapes of the light input and outputsurfaces may be chosen to match, respectively, the shapes of the lightemitter and the surface receiving the outputted light. This matchingfacilitates high efficiency, with an exceptionally high proportion ofthe light from the light emitter light reaching the receiving surface.In addition, the reflector may be formed in one or more unitary bodiesof material, which can provide advantages for simplifying manufacturingand for providing a compact structure, while blocking light leakagebetween reflectors. In addition, other associated structures, such asmask openings, may also be formed in unitary bodies that may be overlaidthe reflectors, which can simplify the manufacture of those structures,and the subsequent assembly of those structures into an integratedoptical system. In some embodiments, the reflector and lens areconfigured to achieve 4-D light shaping.

Reference will now be made to the Figures, in which like referencenumbers refer to like features throughout.

With reference to FIG. 1 , an augmented reality scene 1 is depicted.Modern computing and display technologies have facilitated thedevelopment of systems for so called “virtual reality” or “augmentedreality” experiences, in which digitally reproduced images or portionsthereof are presented to a user in a manner wherein they seem to be, ormay be perceived as, real. A virtual reality, or “VR”, scenariotypically involves the presentation of digital or virtual imageinformation without transparency to other actual real-world visualinput; an augmented reality, or “AR”, scenario typically involvespresentation of digital or virtual image information as an augmentationto visualization of the actual world around the user. A mixed reality,or “MR”, scenario is a type of AR scenario and typically involvesvirtual objects that are integrated into, and responsive to, the naturalworld. For example, an MR scenario may include AR image content thatappears to be blocked by or is otherwise perceived to interact withobjects in the real world. FIG. 1 illustrates an augmented reality scene1 in which the user of an AR technology sees a real-world park-likesetting 20 featuring people, trees, buildings in the background, and aconcrete platform 30. The user also perceives that he “sees” “virtualcontent” such as a robot statue 40 standing upon the real-world platform1120, and a flying cartoon-like avatar character 50 which seems to be apersonification of a bumble bee. These elements 50, 40 are “virtual” inthat they do not exist in the real world. Because the human visualperception system is complex, it is challenging to produce AR technologythat facilitates a comfortable, natural-feeling, rich presentation ofvirtual image elements amongst other virtual or real-world imageryelements.

FIG. 2 illustrates an example of wearable display system 60. The displaysystem 60 includes a display 70, and various mechanical and electronicmodules and systems to support the functioning of that display 70. Thedisplay 70 may be coupled to a frame 80, which is wearable by a displaysystem user or viewer 90 and which is configured to position the display70 in front of the eyes of the user 90. The display 70 may be consideredeyewear in some embodiments. In some embodiments, a speaker 100 iscoupled to the frame 80 and configured to be positioned adjacent the earcanal of the user 90 (in some embodiments, another speaker, not shown,may optionally be positioned adjacent the other ear canal of the user toprovide stereo/shapeable sound control). The display system may alsoinclude one or more microphones 110 or other devices to detect sound. Insome embodiments, the microphone is configured to allow the user toprovide inputs or commands to the system 60 (e.g., the selection ofvoice menu commands, natural language questions, etc.), and/or may allowaudio communication with other persons (e.g., with other users ofsimilar display systems. The microphone may further be configured as aperipheral sensor to collect audio data (e.g., sounds from the userand/or environment). In some embodiments, the display system may alsoinclude a peripheral sensor 120 a, which may be separate from the frame80 and attached to the body of the user 90 (e.g., on the head, torso, anextremity, etc. of the user 90). The peripheral sensor 120 a may beconfigured to acquire data characterizing a physiological state of theuser 90 in some embodiments. For example, the sensor 120 a may be anelectrode.

With continued reference to FIG. 2 , the display 70 is operativelycoupled by communications link 130, such as by a wired lead or wirelessconnectivity, to a local data processing module 140 which may be mountedin a variety of configurations, such as fixedly attached to the frame80, fixedly attached to a helmet or hat worn by the user, embedded inheadphones, or otherwise removably attached to the user 90 (e.g., in abackpack-style configuration, in a belt-coupling style configuration).Similarly, the sensor 120 a may be operatively coupled by communicationslink 120 b, e.g., a wired lead or wireless connectivity, to the localprocessor and data module 140. The local processing and data module 140may comprise a hardware processor, as well as digital memory, such asnon-volatile memory (e.g., flash memory or hard disk drives), both ofwhich may be utilized to assist in the processing, caching, and storageof data. The data include data a) captured from sensors (which may be,e.g., operatively coupled to the frame 80 or otherwise attached to theuser 90), such as image capture devices (such as cameras), microphones,inertial measurement units, accelerometers, compasses, GPS units, radiodevices, gyros, and/or other sensors disclosed herein; and/or b)acquired and/or processed using remote processing module 150 and/orremote data repository 160 (including data relating to virtual content),possibly for passage to the display 70 after such processing orretrieval. The local processing and data module 140 may be operativelycoupled by communication links 170, 180, such as via a wired or wirelesscommunication links, to the remote processing module 150 and remote datarepository 160 such that these remote modules 150, 160 are operativelycoupled to each other and available as resources to the local processingand data module 140. In some embodiments, the local processing and datamodule 140 may include one or more of the image capture devices,microphones, inertial measurement units, accelerometers, compasses, GPSunits, radio devices, and/or gyros. In some other embodiments, one ormore of these sensors may be attached to the frame 80, or may bestandalone structures that communicate with the local processing anddata module 140 by wired or wireless communication pathways.

With continued reference to FIG. 2 , in some embodiments, the remoteprocessing module 150 may comprise one or more processors configured toanalyze and process data and/or image information. In some embodiments,the remote data repository 160 may comprise a digital data storagefacility, which may be available through the internet or othernetworking configuration in a “cloud” resource configuration. In someembodiments, the remote data repository 160 may include one or moreremote servers, which provide information, e.g., information forgenerating augmented reality content, to the local processing and datamodule 140 and/or the remote processing module 150. In some embodiments,all data is stored and all computations are performed in the localprocessing and data module, allowing fully autonomous use from a remotemodule.

With reference now to FIG. 3 , the perception of an image as being“three-dimensional” or “3-D” may be achieved by providing slightlydifferent presentations of the image to each eye of the viewer. FIG. 3illustrates a conventional display system for simulatingthree-dimensional imagery for a user. Two distinct images 190, 200—onefor each eye 210, 220—are outputted to the user. The images 190, 200 arespaced from the eyes 210, 220 by a distance 230 along an optical orz-axis that is parallel to the line of sight of the viewer. The images190, 200 are flat and the eyes 210, 220 may focus on the images byassuming a single accommodated state. Such 3-D display systems rely onthe human visual system to combine the images 190, 200 to provide aperception of depth and/or scale for the combined image.

It will be appreciated, however, that the human visual system is morecomplicated and providing a realistic perception of depth is morechallenging. For example, many viewers of conventional “3-D” displaysystems find such systems to be uncomfortable or may not perceive asense of depth at all. Without being limited by theory, it is believedthat viewers of an object may perceive the object as being“three-dimensional” due to a combination of vergence and accommodation.Vergence movements (i.e., rotation of the eyes so that the pupils movetoward or away from each other to converge the lines of sight of theeyes to fixate upon an object) of the two eyes relative to each otherare closely associated with focusing (or “accommodation”) of the lensesand pupils of the eyes. Under normal conditions, changing the focus ofthe lenses of the eyes, or accommodating the eyes, to change focus fromone object to another object at a different distance will automaticallycause a matching change in vergence to the same distance, under arelationship known as the “accommodation-vergence reflex,” as well aspupil dilation or constriction. Likewise, a change in vergence willtrigger a matching change in accommodation of lens shape and pupil size,under normal conditions. As noted herein, many stereoscopic or “3-D”display systems display a scene using slightly different presentations(and, so, slightly different images) to each eye such that athree-dimensional perspective is perceived by the human visual system.Such systems are uncomfortable for many viewers, however, since they,among other things, simply provide different presentations of a scene,but with the eyes viewing all the image information at a singleaccommodated state, and work against the “accommodation-vergencereflex.” Display systems that provide a better match betweenaccommodation and vergence may form more realistic and comfortablesimulations of three-dimensional imagery.

FIG. 4 illustrates aspects of an approach for simulatingthree-dimensional imagery using multiple depth planes. With reference toFIG. 4 , objects at various distances from eyes 210, 220 on the z-axisare accommodated by the eyes 210, 220 so that those objects are infocus. The eyes 210, 220 assume particular accommodated states to bringinto focus objects at different distances along the z-axis.Consequently, a particular accommodated state may be said to beassociated with a particular one of depth planes 240, with has anassociated focal distance, such that objects or parts of objects in aparticular depth plane are in focus when the eye is in the accommodatedstate for that depth plane. In some embodiments, three-dimensionalimagery may be simulated by providing different presentations of animage for each of the eyes 210, 220, and also by providing differentpresentations of the image corresponding to each of the depth planes.While shown as being separate for clarity of illustration, it will beappreciated that the fields of view of the eyes 210, 220 may overlap,for example, as distance along the z-axis increases. In addition, whileshown as flat for ease of illustration, it will be appreciated that thecontours of a depth plane may be curved in physical space, such that allfeatures in a depth plane are in focus with the eye in a particularaccommodated state.

The distance between an object and the eye 210 or 220 may also changethe amount of divergence of light from that object, as viewed by thateye. FIGS. 5A-5C illustrate relationships between distance and thedivergence of light rays. The distance between the object and the eye210 is represented by, in order of decreasing distance, R1, R2, and R3.As shown in FIGS. 5A-5C, the light rays become more divergent asdistance to the object decreases. As distance increases, the light raysbecome more collimated. Stated another way, it may be said that thelight field produced by a point (the object or a part of the object) hasa spherical wavefront curvature, which is a function of how far away thepoint is from the eye of the user. The curvature increases withdecreasing distance between the object and the eye 210. Consequently, atdifferent depth planes, the degree of divergence of light rays is alsodifferent, with the degree of divergence increasing with decreasingdistance between depth planes and the viewer's eye 210. While only asingle eye 210 is illustrated for clarity of illustration in FIGS. 5A-5Cand other figures herein, it will be appreciated that the discussionsregarding eye 210 may be applied to both eyes 210 and 220 of a viewer.

Without being limited by theory, it is believed that the human eyetypically can interpret a finite number of depth planes to provide depthperception. Consequently, a highly believable simulation of perceiveddepth may be achieved by providing, to the eye, different presentationsof an image corresponding to each of these limited number of depthplanes. The different presentations may be separately focused by theviewer's eyes, thereby helping to provide the user with depth cues basedon the accommodation of the eye required to bring into focus differentimage features for the scene located on different depth plane and/orbased on observing different image features on different depth planesbeing out of focus.

FIG. 6 illustrates an example of a waveguide stack for outputting imageinformation to a user. A display system 250 includes a stack ofwaveguides, or stacked waveguide assembly, 260 that may be utilized toprovide three-dimensional perception to the eye/brain using a pluralityof waveguides 270, 280, 290, 300, 310. In some embodiments, the displaysystem 250 is the system 60 of FIG. 2 , with FIG. 6 schematicallyshowing some parts of that system 60 in greater detail. For example, thewaveguide assembly 260 may be part of the display 70 of FIG. 2 . It willbe appreciated that the display system 250 may be considered a lightfield display in some embodiments. In addition, the waveguide assembly260 may also be referred to as an eyepiece.

With continued reference to FIG. 6 , the waveguide assembly 260 may alsoinclude a plurality of features 320, 330, 340, 350 between thewaveguides. In some embodiments, the features 320, 330, 340, 350 may beone or more lenses. The waveguides 270, 280, 290, 300, 310 and/or theplurality of lenses 320, 330, 340, 350 may be configured to send imageinformation to the eye with various levels of wavefront curvature orlight ray divergence. Each waveguide level may be associated with aparticular depth plane and may be configured to output image informationcorresponding to that depth plane. Image injection devices 360, 370,380, 390, 400 may function as a source of light for the waveguides andmay be utilized to inject image information into the waveguides 270,280, 290, 300, 310, each of which may be configured, as describedherein, to distribute incoming light across each respective waveguide,for output toward the eye 210. Light exits an output surface 410, 420,430, 440, 450 of the image injection devices 360, 370, 380, 390, 400 andis injected into a corresponding input surface 460, 470, 480, 490, 500of the waveguides 270, 280, 290, 300, 310. In some embodiments, the eachof the input surfaces 460, 470, 480, 490, 500 may be an edge of acorresponding waveguide, or may be part of a major surface of thecorresponding waveguide (that is, one of the waveguide surfaces directlyfacing the world 510 or the viewer's eye 210). In some embodiments, asingle beam of light (e.g. a collimated beam) may be injected into eachwaveguide to output an entire field of cloned collimated beams that aredirected toward the eye 210 at particular angles (and amounts ofdivergence) corresponding to the depth plane associated with aparticular waveguide. In some embodiments, a single one of the imageinjection devices 360, 370, 380, 390, 400 may be associated with andinject light into a plurality (e.g., three) of the waveguides 270, 280,290, 300, 310.

In some embodiments, the image injection devices 360, 370, 380, 390, 400are discrete displays that each produce image information for injectioninto a corresponding waveguide 270, 280, 290, 300, 310, respectively. Insome other embodiments, the image injection devices 360, 370, 380, 390,400 are the output ends of a single multiplexed display which may, e.g.,pipe image information via one or more optical conduits (such as fiberoptic cables) to each of the image injection devices 360, 370, 380, 390,400. It will be appreciated that the image information provided by theimage injection devices 360, 370, 380, 390, 400 may include light ofdifferent wavelengths, or colors (e.g., different component colors, asdiscussed herein).

In some embodiments, the light injected into the waveguides 270, 280,290, 300, 310 is provided by a light projector system 520, whichcomprises a light module 540, which may include a light emitter, such asa light emitting diode (LED). The light from the light module 540 may bedirected to and modified by a light modulator 530, e.g., a spatial lightmodulator, via a beam splitter 550. The light modulator 530 may beconfigured to change the perceived intensity of the light injected intothe waveguides 270, 280, 290, 300, 310. Examples of spatial lightmodulators include liquid crystal displays (LCD) including a liquidcrystal on silicon (LCOS) displays. It will be appreciated that theimage injection devices 360, 370, 380, 390, 400 are illustratedschematically and, in some embodiments, these image injection devicesmay represent different light paths and locations in a common projectionsystem configured to output light into associated ones of the waveguides270, 280, 290, 300, 310.

In some embodiments, the display system 250 may be a scanning fiberdisplay comprising one or more scanning fibers configured to projectlight in various patterns (e.g., raster scan, spiral scan, Lissajouspatterns, etc.) into one or more waveguides 270, 280, 290, 300, 310 andultimately to the eye 210 of the viewer. In some embodiments, theillustrated image injection devices 360, 370, 380, 390, 400 mayschematically represent a single scanning fiber or a bundle of scanningfibers configured to inject light into one or a plurality of thewaveguides 270, 280, 290, 300, 310. In some other embodiments, theillustrated image injection devices 360, 370, 380, 390, 400 mayschematically represent a plurality of scanning fibers or a plurality ofbundles of scanning fibers, each of which are configured to inject lightinto an associated one of the waveguides 270, 280, 290, 300, 310. Itwill be appreciated that one or more optical fibers may be configured totransmit light from the light module 540 to the one or more waveguides270, 280, 290, 300, 310. It will be appreciated that one or moreintervening optical structures may be provided between the scanningfiber, or fibers, and the one or more waveguides 270, 280, 290, 300, 310to, e.g., redirect light exiting the scanning fiber into the one or morewaveguides 270, 280, 290, 300, 310.

A controller 560 controls the operation of one or more of the stackedwaveguide assembly 260, including operation of the image injectiondevices 360, 370, 380, 390, 400, the light source 540, and the lightmodulator 530. In some embodiments, the controller 560 is part of thelocal data processing module 140. The controller 560 includesprogramming (e.g., instructions in a non-transitory medium) thatregulates the timing and provision of image information to thewaveguides 270, 280, 290, 300, 310 according to, e.g., any of thevarious schemes disclosed herein. In some embodiments, the controllermay be a single integral device, or a distributed system connected bywired or wireless communication channels. The controller 560 may be partof the processing modules 140 or 150 (FIG. 2 ) in some embodiments.

With continued reference to FIG. 6 , the waveguides 270, 280, 290, 300,310 may be configured to propagate light within each respectivewaveguide by total internal reflection (TIR). The waveguides 270, 280,290, 300, 310 may each be planar or have another shape (e.g., curved),with major top and bottom surfaces and edges extending between thosemajor top and bottom surfaces. In the illustrated configuration, thewaveguides 270, 280, 290, 300, 310 may each include out-coupling opticalelements 570, 580, 590, 600, 610 that are configured to extract lightout of a waveguide by redirecting the light, propagating within eachrespective waveguide, out of the waveguide to output image informationto the eye 210. Extracted light may also be referred to as out-coupledlight and the out-coupling optical elements light may also be referredto light extracting optical elements. An extracted beam of light may beoutputted by the waveguide at locations at which the light propagatingin the waveguide strikes a light extracting optical element. Theout-coupling optical elements 570, 580, 590, 600, 610 may, for example,be gratings, including diffractive optical features, as discussedfurther herein. While illustrated disposed at the bottom major surfacesof the waveguides 270, 280, 290, 300, 310, for ease of description anddrawing clarity, in some embodiments, the out-coupling optical elements570, 580, 590, 600, 610 may be disposed at the top and/or bottom majorsurfaces, and/or may be disposed directly in the volume of thewaveguides 270, 280, 290, 300, 310, as discussed further herein. In someembodiments, the out-coupling optical elements 570, 580, 590, 600, 610may be formed in a layer of material that is attached to a transparentsubstrate to form the waveguides 270, 280, 290, 300, 310. In some otherembodiments, the waveguides 270, 280, 290, 300, 310 may be a monolithicpiece of material and the out-coupling optical elements 570, 580, 590,600, 610 may be formed on a surface and/or in the interior of that pieceof material.

With continued reference to FIG. 6 , as discussed herein, each waveguide270, 280, 290, 300, 310 is configured to output light to form an imagecorresponding to a particular depth plane. For example, the waveguide270 nearest the eye may be configured to deliver collimated light (whichwas injected into such waveguide 270), to the eye 210. The collimatedlight may be representative of the optical infinity focal plane. Thenext waveguide up 280 may be configured to send out collimated lightwhich passes through the first lens 350 (e.g., a negative lens) beforeit can reach the eye 210; such first lens 350 may be configured tocreate a slight convex wavefront curvature so that the eye/braininterprets light coming from that next waveguide up 280 as coming from afirst focal plane closer inward toward the eye 210 from opticalinfinity. Similarly, the third up waveguide 290 passes its output lightthrough both the first 350 and second 340 lenses before reaching the eye210; the combined optical power of the first 350 and second 340 lensesmay be configured to create another incremental amount of wavefrontcurvature so that the eye/brain interprets light coming from the thirdwaveguide 290 as coming from a second focal plane that is even closerinward toward the person from optical infinity than was light from thenext waveguide up 280.

The other waveguide layers 300, 310 and lenses 330, 320 are similarlyconfigured, with the highest waveguide 310 in the stack sending itsoutput through all of the lenses between it and the eye for an aggregatefocal power representative of the closest focal plane to the person. Tocompensate for the stack of lenses 320, 330, 340, 350 whenviewing/interpreting light coming from the world 510 on the other sideof the stacked waveguide assembly 260, a compensating lens layer 620 maybe disposed at the top of the stack to compensate for the aggregatepower of the lens stack 320, 330, 340, 350 below. Such a configurationprovides as many perceived focal planes as there are availablewaveguide/lens pairings. Both the out-coupling optical elements of thewaveguides and the focusing aspects of the lenses may be static (i.e.,not dynamic or electro-active). In some alternative embodiments, eitheror both may be dynamic using electro-active features.

In some embodiments, two or more of the waveguides 270, 280, 290, 300,310 may have the same associated depth plane. For example, multiplewaveguides 270, 280, 290, 300, 310 may be configured to output imagesset to the same depth plane, or multiple subsets of the waveguides 270,280, 290, 300, 310 may be configured to output images set to the sameplurality of depth planes, with one set for each depth plane. This canprovide advantages for forming a tiled image to provide an expandedfield of view at those depth planes.

With continued reference to FIG. 6 , the out-coupling optical elements570, 580, 590, 600, 610 may be configured to both redirect light out oftheir respective waveguides and to output this light with theappropriate amount of divergence or collimation for a particular depthplane associated with the waveguide. As a result, waveguides havingdifferent associated depth planes may have different configurations ofout-coupling optical elements 570, 580, 590, 600, 610, which outputlight with a different amount of divergence depending on the associateddepth plane. In some embodiments, the light extracting optical elements570, 580, 590, 600, 610 may be volumetric or surface features, which maybe configured to output light at specific angles. For example, the lightextracting optical elements 570, 580, 590, 600, 610 may be volumeholograms, surface holograms, and/or diffraction gratings. In someembodiments, the features 320, 330, 340, 350 may not be lenses; rather,they may simply be spacers (e.g., cladding layers and/or structures forforming air gaps).

In some embodiments, the out-coupling optical elements 570, 580, 590,600, 610 are diffractive features that form a diffraction pattern, or“diffractive optical element” (also referred to herein as a “DOE”).Preferably, the DOE's have a sufficiently low diffraction efficiency sothat only a portion of the light of the beam is deflected away towardthe eye 210 with each intersection of the DOE, while the rest continuesto move through a waveguide via TIR. The light carrying the imageinformation is thus divided into a number of related exit beams thatexit the waveguide at a multiplicity of locations and the result is afairly uniform pattern of exit emission toward the eye 210 for thisparticular collimated beam bouncing around within a waveguide.

In some embodiments, one or more DOEs may be switchable between “on”states in which they actively diffract, and “off” states in which theydo not significantly diffract. For instance, a switchable DOE maycomprise a layer of polymer dispersed liquid crystal, in whichmicrodroplets comprise a diffraction pattern in a host medium, and therefractive index of the microdroplets may be switched to substantiallymatch the refractive index of the host material (in which case thepattern does not appreciably diffract incident light) or themicrodroplet may be switched to an index that does not match that of thehost medium (in which case the pattern actively diffracts incidentlight).

In some embodiments, a camera assembly 630 (e.g., a digital camera,including visible light and infrared light cameras) may be provided tocapture images of the eye 210 and/or tissue around the eye 210 to, e.g.,detect user inputs and/or to monitor the physiological state of theuser. As used herein, a camera may be any image capture device. In someembodiments, the camera assembly 630 may include an image capture deviceand a light source to project light (e.g., infrared light) to the eye,which may then be reflected by the eye and detected by the image capturedevice. In some embodiments, the camera assembly 630 may be attached tothe frame 80 (FIG. 2 ) and may be in electrical communication with theprocessing modules 140 and/or 150, which may process image informationfrom the camera assembly 630. In some embodiments, one camera assembly630 may be utilized for each eye, to separately monitor each eye.

With reference now to FIG. 7 , an example of exit beams outputted by awaveguide is shown. One waveguide is illustrated, but it will beappreciated that other waveguides in the waveguide assembly 260 (FIG. 6) may function similarly, where the waveguide assembly 260 includesmultiple waveguides. Light 640 is injected into the waveguide 270 at theinput surface 460 of the waveguide 270 and propagates within thewaveguide 270 by TIR. At points where the light 640 impinges on the DOE570, a portion of the light exits the waveguide as exit beams 650. Theexit beams 650 are illustrated as substantially parallel but, asdiscussed herein, they may also be redirected to propagate to the eye210 at an angle (e.g., forming divergent exit beams), depending on thedepth plane associated with the waveguide 270. It will be appreciatedthat substantially parallel exit beams may be indicative of a waveguidewith out-coupling optical elements that out-couple light to form imagesthat appear to be set on a depth plane at a large distance (e.g.,optical infinity) from the eye 210. Other waveguides or other sets ofout-coupling optical elements may output an exit beam pattern that ismore divergent, which would require the eye 210 to accommodate to acloser distance to bring it into focus on the retina and would beinterpreted by the brain as light from a distance closer to the eye 210than optical infinity.

In some embodiments, a full color image may be formed at each depthplane by overlaying images in each of the component colors, e.g., threeor more component colors. FIG. 8 illustrates an example of a stackedwaveguide assembly in which each depth plane includes images formedusing multiple different component colors. The illustrated embodimentshows depth planes 240 a-240 f, although more or fewer depths are alsocontemplated. Each depth plane may have three or more component colorimages associated with it, including: a first image of a first color, G;a second image of a second color, R; and a third image of a third color,B. Different depth planes are indicated in the figure by differentnumbers for diopters (dpt) following the letters G, R, and B. Just asexamples, the numbers following each of these letters indicate diopters(1/m), or inverse distance of the depth plane from a viewer, and eachbox in the figures represents an individual component color image. Insome embodiments, to account for differences in the eye's focusing oflight of different wavelengths, the exact placement of the depth planesfor different component colors may vary. For example, differentcomponent color images for a given depth plane may be placed on depthplanes corresponding to different distances from the user. Such anarrangement may increase visual acuity and user comfort and/or maydecrease chromatic aberrations.

In some embodiments, light of each component color may be outputted by asingle dedicated waveguide and, consequently, each depth plane may havemultiple waveguides associated with it. In such embodiments, each box inthe figures including the letters G, R, or B may be understood torepresent an individual waveguide, and three waveguides may be providedper depth plane where three component color images are provided perdepth plane. While the waveguides associated with each depth plane areshown adjacent to one another in this drawing for ease of description,it will be appreciated that, in a physical device, the waveguides mayall be arranged in a stack with one waveguide per level. In some otherembodiments, multiple component colors may be outputted by the samewaveguide, such that, e.g., only a single waveguide may be provided perdepth plane.

With continued reference to FIG. 8 , in some embodiments, G is the colorgreen, R is the color red, and B is the color blue. In some otherembodiments, other colors associated with other wavelengths of light,including magenta and cyan, may be used in addition to or may replaceone or more of red, green, or blue.

It will be appreciated that references to a given color of lightthroughout this disclosure will be understood to encompass light of oneor more wavelengths within a range of wavelengths of light that areperceived by a viewer as being of that given color. For example, redlight may include light of one or more wavelengths in the range of about620-780 nm, green light may include light of one or more wavelengths inthe range of about 492-577 nm, and blue light may include light of oneor more wavelengths in the range of about 435-493 nm.

In some embodiments, the light source 540 (FIG. 6 ) may be configured toemit light of one or more wavelengths outside the visual perceptionrange of the viewer, for example, infrared and/or ultravioletwavelengths. In addition, the in-coupling, out-coupling, and other lightredirecting structures of the waveguides of the display 250 may beconfigured to direct and emit this light out of the display towards theuser's eye 210, e.g., for imaging and/or user stimulation applications.

With reference now to FIG. 9A, in some embodiments, light impinging on awaveguide may need to be redirected to in-couple that light into thewaveguide. An in-coupling optical element may be used to redirect andin-couple the light into its corresponding waveguide. FIG. 9Aillustrates a cross-sectional side view of an example of a plurality orset 660 of stacked waveguides that each includes an in-coupling opticalelement. The waveguides may each be configured to output light of one ormore different wavelengths, or one or more different ranges ofwavelengths. It will be appreciated that the stack 660 may correspond tothe stack 260 (FIG. 6 ) and the illustrated waveguides of the stack 660may correspond to part of the plurality of waveguides 270, 280, 290,300, 310, except that light from one or more of the image injectiondevices 360, 370, 380, 390, 400 is injected into the waveguides from aposition that requires light to be redirected for in-coupling.

The illustrated set 660 of stacked waveguides includes waveguides 670,680, and 690. Each waveguide includes an associated in-coupling opticalelement (which may also be referred to as a light input area on thewaveguide), with, e.g., in-coupling optical element 700 disposed on amajor surface (e.g., an upper major surface) of waveguide 670,in-coupling optical element 710 disposed on a major surface (e.g., anupper major surface) of waveguide 680, and in-coupling optical element720 disposed on a major surface (e.g., an upper major surface) ofwaveguide 690. In some embodiments, one or more of the in-couplingoptical elements 700, 710, 720 may be disposed on the bottom majorsurface of the respective waveguide 670, 680, 690 (particularly wherethe one or more in-coupling optical elements are reflective, deflectingoptical elements). As illustrated, the in-coupling optical elements 700,710, 720 may be disposed on the upper major surface of their respectivewaveguide 670, 680, 690 (or the top of the next lower waveguide),particularly where those in-coupling optical elements are transmissive,deflecting optical elements. In some embodiments, the in-couplingoptical elements 700, 710, 720 may be disposed in the body of therespective waveguide 670, 680, 690. In some embodiments, as discussedherein, the in-coupling optical elements 700, 710, 720 are wavelengthselective, such that they selectively redirect one or more wavelengthsof light, while transmitting other wavelengths of light. Whileillustrated on one side or corner of their respective waveguide 670,680, 690, it will be appreciated that the in-coupling optical elements700, 710, 720 may be disposed in other areas of their respectivewaveguide 670, 680, 690 in some embodiments.

As illustrated, the in-coupling optical elements 700, 710, 720 may belaterally offset from one another. In some embodiments, each in-couplingoptical element may be offset such that it receives light without thatlight passing through another in-coupling optical element. For example,each in-coupling optical element 700, 710, 720 may be configured toreceive light from a different image injection device 360, 370, 380,390, and 400 as shown in FIG. 6 , and may be separated (e.g., laterallyspaced apart) from other in-coupling optical elements 700, 710, 720 suchthat it substantially does not receive light from the other ones of thein-coupling optical elements 700, 710, 720.

Each waveguide also includes associated light distributing elements,with, e.g., light distributing elements 730 disposed on a major surface(e.g., a top major surface) of waveguide 670, light distributingelements 740 disposed on a major surface (e.g., a top major surface) ofwaveguide 680, and light distributing elements 750 disposed on a majorsurface (e.g., a top major surface) of waveguide 690. In some otherembodiments, the light distributing elements 730, 740, 750, may bedisposed on a bottom major surface of associated waveguides 670, 680,690, respectively. In some other embodiments, the light distributingelements 730, 740, 750, may be disposed on both top and bottom majorsurface of associated waveguides 670, 680, 690, respectively; or thelight distributing elements 730, 740, 750, may be disposed on differentones of the top and bottom major surfaces in different associatedwaveguides 670, 680, 690, respectively.

The waveguides 670, 680, 690 may be spaced apart and separated by, e.g.,gas, liquid, and/or solid layers of material. For example, asillustrated, layer 760 a may separate waveguides 670 and 680; and layer760 b may separate waveguides 680 and 690. In some embodiments, thelayers 760 a and 760 b are formed of low refractive index materials(that is, materials having a lower refractive index than the materialforming the immediately adjacent one of waveguides 670, 680, 690).Preferably, the refractive index of the material forming the layers 760a, 760 b is 0.05 or more, or 0.10 or less than the refractive index ofthe material forming the waveguides 670, 680, 690. Advantageously, thelower refractive index layers 760 a, 760 b may function as claddinglayers that facilitate total internal reflection (TIR) of light throughthe waveguides 670, 680, 690 (e.g., TIR between the top and bottom majorsurfaces of each waveguide). In some embodiments, the layers 760 a, 760b are formed of air. While not illustrated, it will be appreciated thatthe top and bottom of the illustrated set 660 of waveguides may includeimmediately neighboring cladding layers.

Preferably, for ease of manufacturing and other considerations, thematerial forming the waveguides 670, 680, 690 are similar or the same,and the material forming the layers 760 a, 760 b are similar or thesame. In some embodiments, the material forming the waveguides 670, 680,690 may be different between one or more waveguides, and/or the materialforming the layers 760 a, 760 b may be different, while still holding tothe various refractive index relationships noted above.

With continued reference to FIG. 9A, light rays 770, 780, 790 areincident on the set 660 of waveguides. It will be appreciated that thelight rays 770, 780, 790 may be injected into the waveguides 670, 680,690 by one or more image injection devices 360, 370, 380, 390, 400 (FIG.6 ).

In some embodiments, the light rays 770, 780, 790 have differentproperties, e.g., different wavelengths or different ranges ofwavelengths, which may correspond to different colors. The in-couplingoptical elements 700, 710, 720 each deflect the incident light such thatthe light propagates through a respective one of the waveguides 670,680, 690 by TIR. In some embodiments, the incoupling optical elements700, 710, 720 each selectively deflect one or more particularwavelengths of light, while transmitting other wavelengths to anunderlying waveguide and associated incoupling optical element.

For example, in-coupling optical element 700 may be configured todeflect ray 770, which has a first wavelength or range of wavelengths,while transmitting rays 780 and 790, which have different second andthird wavelengths or ranges of wavelengths, respectively. Thetransmitted ray 780 impinges on and is deflected by the in-couplingoptical element 710, which is configured to deflect light of a secondwavelength or range of wavelengths. The ray 790 is deflected by thein-coupling optical element 720, which is configured to selectivelydeflect light of third wavelength or range of wavelengths.

With continued reference to FIG. 9A, the deflected light rays 770, 780,790 are deflected so that they propagate through a correspondingwaveguide 670, 680, 690; that is, the in-coupling optical elements 700,710, 720 of each waveguide deflects light into that correspondingwaveguide 670, 680, 690 to in-couple light into that correspondingwaveguide. The light rays 770, 780, 790 are deflected at angles thatcause the light to propagate through the respective waveguide 670, 680,690 by TIR. The light rays 770, 780, 790 propagate through therespective waveguide 670, 680, 690 by TIR until impinging on thewaveguide's corresponding light distributing elements 730, 740, 750.

With reference now to FIG. 9B, a perspective view of an example of theplurality of stacked waveguides of FIG. 9A is illustrated. As notedabove, the in-coupled light rays 770, 780, 790, are deflected by thein-coupling optical elements 700, 710, 720, respectively, and thenpropagate by TIR within the waveguides 670, 680, 690, respectively. Thelight rays 770, 780, 790 then impinge on the light distributing elements730, 740, 750, respectively. The light distributing elements 730, 740,750 deflect the light rays 770, 780, 790 so that they propagate towardsthe out-coupling optical elements 800, 810, 820, respectively.

In some embodiments, the light distributing elements 730, 740, 750 areorthogonal pupil expanders (OPE's). In some embodiments, the OPE'sdeflect or distribute light to the out-coupling optical elements 800,810, 820 and, in some embodiments, may also increase the beam or spotsize of this light as it propagates to the out-coupling opticalelements. In some embodiments, the light distributing elements 730, 740,750 may be omitted and the in-coupling optical elements 700, 710, 720may be configured to deflect light directly to the out-coupling opticalelements 800, 810, 820. For example, with reference to FIG. 9A, thelight distributing elements 730, 740, 750 may be replaced without-coupling optical elements 800, 810, 820, respectively. In someembodiments, the out-coupling optical elements 800, 810, 820 are exitpupils (EP's) or exit pupil expanders (EPE's) that direct light in aviewer's eye 210 (FIG. 7 ). It will be appreciated that the OPE's may beconfigured to increase the dimensions of the eye box in at least oneaxis and the EPE's may be to increase the eye box in an axis crossing,e.g., orthogonal to, the axis of the OPEs. For example, each OPE may beconfigured to redirect a portion of the light striking the OPE to an EPEof the same waveguide, while allowing the remaining portion of the lightto continue to propagate down the waveguide. Upon impinging on the OPEagain, another portion of the remaining light is redirected to the EPE,and the remaining portion of that portion continues to propagate furtherdown the waveguide, and so on. Similarly, upon striking the EPE, aportion of the impinging light is directed out of the waveguide towardsthe user, and a remaining portion of that light continues to propagatethrough the waveguide until it strikes the EP again, at which timeanother portion of the impinging light is directed out of the waveguide,and so on. Consequently, a single beam of incoupled light may be“replicated” each time a portion of that light is redirected by an OPEor EPE, thereby forming a field of cloned beams of light, as shown inFIG. 6 . In some embodiments, the OPE and/or EPE may be configured tomodify a size of the beams of light.

Accordingly, with reference to FIGS. 9A and 9B, in some embodiments, theset 660 of waveguides includes waveguides 670, 680, 690; in-couplingoptical elements 700, 710, 720; light distributing elements (e.g.,OPE's) 730, 740, 750; and out-coupling optical elements (e.g., EP's)800, 810, 820 for each component color. The waveguides 670, 680, 690 maybe stacked with an air gap/cladding layer between each one. Thein-coupling optical elements 700, 710, 720 redirect or deflect incidentlight (with different in-coupling optical elements receiving light ofdifferent wavelengths) into its waveguide. The light then propagates atan angle which will result in TIR within the respective waveguide 670,680, 690. In the example shown, light ray 770 (e.g., blue light) isdeflected by the first in-coupling optical element 700, and thencontinues to bounce down the waveguide, interacting with the lightdistributing element (e.g., OPE's) 730 and then the out-coupling opticalelement (e.g., EPs) 800, in a manner described earlier. The light rays780 and 790 (e.g., green and red light, respectively) will pass throughthe waveguide 670, with light ray 780 impinging on and being deflectedby in-coupling optical element 710. The light ray 780 then bounces downthe waveguide 680 via TIR, proceeding on to its light distributingelement (e.g., OPEs) 740 and then the out-coupling optical element(e.g., EP's) 810. Finally, light ray 790 (e.g., red light) passesthrough the waveguide 690 to impinge on the light in-coupling opticalelements 720 of the waveguide 690. The light in-coupling opticalelements 720 deflect the light ray 790 such that the light raypropagates to light distributing element (e.g., OPEs) 750 by TIR, andthen to the out-coupling optical element (e.g., EPs) 820 by TIR. Theout-coupling optical element 820 then finally out-couples the light ray790 to the viewer, who also receives the out-coupled light from theother waveguides 670, 680.

FIG. 9C illustrates a top-down plan view of an example of the pluralityof stacked waveguides of FIGS. 9A and 9B. As illustrated, the waveguides670, 680, 690, along with each waveguide's associated light distributingelement 730, 740, 750 and associated out-coupling optical element 800,810, 820, may be vertically aligned. However, as discussed herein, thein-coupling optical elements 700, 710, 720 are not vertically aligned;rather, the in-coupling optical elements are preferably non-overlapping(e.g., laterally spaced apart as seen in the top-down view). Asdiscussed further herein, this nonoverlapping spatial arrangementfacilitates the injection of light from different resources intodifferent waveguides on a one-to-one basis, thereby allowing a specificlight source to be uniquely coupled to a specific waveguide. In someembodiments, arrangements including nonoverlapping spatially-separatedin-coupling optical elements may be referred to as a shifted pupilsystem, and the in-coupling optical elements within these arrangementsmay correspond to sub pupils.

In some embodiments, light from a light emitter is shaped using areflector and lens. FIG. 10 illustrates an example of a reflector 2000having the profile of a compound parabolic concentrator (CPC). Thereflector 2000 has a light input opening 2002 and a light output opening2004, both of which may be circular. The light input opening may receivelight (e.g., light rays 2010, 2020, 2030) from a light emitter (notshown). The light reflects off the walls 2040 of the reflector to exitthe reflector 2000 through the light output opening 2004. Notably, theoutputted light rays 2010, 2020, 2030 have a high degree of angularuniformity and may exit the reflector substantially parallel to oneanother. Thus, edge rays are collimated by the CPC. The spatialuniformity of the outputted light is poor, however. Undesirably, thelight exiting the reflector 2010 may form hot spots in the shape of aring.

With reference to FIGS. 11-12 , a lens (e.g., a Fourier transform lens)may be utilized to transform the angularly uniform light output of areflector into spatially uniform light output. FIG. 11 illustrates anexample of an optical system 2100 having a reflector 2110 and a lens2120. The reflector 2110 has a light input opening 2102 and a lightoutput opening 2104, with interior sidewalls 2112 a, 2112 b that extendfrom the light input opening 2102 and to the light output opening 2104.The interior sidewalls 2112 a, 2112 b are curved to provide angularlyuniform light output to the lens 2120. In some embodiments, thesidewalls 2112 a, 2112 b have a CPC profile; that is, the curvature ofthe interior sidewalls 2112 a, 2112 b follows that of a compoundparabolic concentrator. It will be appreciated that, in someembodiments, the interior sidewalls 2112 a, 2112 b may follow thecontours of an ellipse, hyperbola, or biconic shape. In some otherembodiments, the interior sidewalls 2112 a, 2112 b may be substantiallylinear, which has been found to provide sufficiently angularly uniformlight output for the lens 21020 to output highly spatially-uniformlight. It will be appreciated that the sidewalls 2112 a, 2112 b areshown as separate in the illustrated cross-section, but, in an actualthree-dimensional reflector, 2112 a and 2112 b are simply opposing sidesof a continuous surface. Preferably, the sidewalls 2112 a, 2112 b arespecular reflectors. In some embodiments, the sidewalls 2112 a, 2112 bmay be formed of a reflective material and/or may be lined with areflective material.

FIG. 12 illustrates an example of the optical system 2100 having a lightemitter 2140 is positioned to emit light into the reflector 2110. Insome embodiments, the light emitter 2140 is outside of the light inputopening. In some other embodiments, the light emitter 2140 is positionedinside of the interior volume of the reflector 2110. In someembodiments, the light emitter 2140 has a lambertian radiation pattern.The light emitter 2140 may be, for example, a light emitting diode(LED), an incandescent light bulb, a fluorescent light bulb, or otherdevice that, e.g., converts electrical energy into light.

With continued reference to FIGS. 11 and 12 , the lens 2120 is proximatethe light output opening 2104. In some embodiments, the lens 2120 islocated forward or directly at the light output opening 2104. In someother embodiments, the lens 2120 may be located inside the reflector2110. Preferably, the distance from the lens 2120 to the light emitter2140 is substantially equal to the focal length of the lens. Inaddition, the distance from the lens to a light modulator (not shown) ispreferably also substantially equal to the focal length of the lens.

It will be appreciated that the illustration of the lens 2120 isschematic. It will also be appreciated that the lens 2120 is an opticaltransmissive structure configured to transform the angularly uniformlight output of the reflector 2110 into spatially uniform light output.For example, as illustrated, light rays 2130 emitted by the lightemitter 2140 are reflected off the sidewalls 2112 a, 2112 b such thatthey propagate in substantially the same direction. The lens 2120 thentransforms this angularly uniform output into the spatially uniformlight 2130 propagating away from the lens 2120. The lens may be asinglet lens in some embodiments. In some other embodiments, the lens2120 may be a compound lens, such as a doublet lens, or a system oflens. Preferably, the lens 2120 extends across substantially theentirety of the area of the light output opening 2104.

FIG. 13 illustrates an example of the light output from the opticalsystem 2100 of FIGS. 11-12 . Light propagates away from the lightemitter 2140 into the lens 2120, and then from the lens 2120 to thelight modulator 209 b. The lens 2120 and the light modulator 209 b arerepresented schematically as lines in this figure. As noted herein, thedistance between the light emitter 2140 and the lens 2120 may be equalto the focal length of the lens, and the distance between the lens 2120and the light modulator 209 b may also be equal to the focal length ofthe lens.

In some embodiments, the reflector 2110 has a light input opening and alight output opening that are the same shape, e.g., circular. In someother embodiments, the shapes of the light input opening and the lightoutput opening are different. FIGS. 14A-14F illustrate examples ofreflectors having light input openings and light output openings withdifferent shapes. The ability to vary the shapes of the light input andoutput openings can provide advantages for efficiently matching lightemitters and light modulators having different shapes or aspect ratios.

FIGS. 14A-14C illustrate the reflector 2110 with a progressiveelliptical shape. FIG. 14A is a perspective view with the light outputopening 2104 facing the viewer. FIG. 14B is a side view looking directlyat the plane 14B of FIG. 14A. FIG. 14C is another side view, this timelooking directly at the plane 14C of FIG. 14A. The plane 14B isorthogonal to the plane 14C. As illustrated, in some embodiments, thelight input opening 2102 of the reflector 2110 has a circular shape,which progressively expands at different rates as seem along the planes14A and 14B, such that the light output opening 2104 has an ellipticalshape. For example, the sidewalls 2112 a and 2112 b expand out at agreater rate than the sidewalls 2112 c and 2112 d. In some embodiments,a notch 2114 may be present at the light input opening 2102 and extendinto the sidewall 2112 c. The notch 2114 may allow connectors (e.g.,wire bonds) for a light emitter (e.g., light emitter 2140, FIG. 12 ) tobe accommodated.

FIGS. 14D-14F illustrate the reflector 2110 with a rectangular lightinput opening 2102. FIG. 14D is a perspective view with the light outputopening 2104 facing the viewer. FIG. 14E is a side view looking directlyat the plane 14E of FIG. 14D. FIG. 14F is another side view, this timelooking directly at the plane 14F of FIG. 14D. The plane 14E isorthogonal to the plane 14F. As illustrated, in some embodiments, thelight input opening 2102 of the reflector 2110 has a rectangular shape(e.g., a square shape), which progressively expands such that the lightoutput opening 2104 has a rectangular shape with different lengths andwidths. It will be appreciated that a square light input opening 2102may be beneficial for mating to a square light emitter, such as manyLED's. On the other hand, in applications where the reflector 2110 isused to provide light to a light modulator 209 b (FIG. 6 ), the lightmodulator 209 b may be configured to generate images at standard aspectratios, in which one dimension is larger than another crossing dimension(e.g., the aspect ratios may be 4:3, 16:9, etc.). As illustrated in FIG.14D, the light output opening 2104 may have two straight sides 2104 a,2104 b joined by two curves sides 2104 c, 2104 d.

With reference to FIGS. 14A-14F, the planes 14A, 14B, 14E, and 14F, aremidplanes that substantially bisect (at least with reference to thelight output opening 2104) the various illustrated embodiments of thereflector 2110. It will be appreciated that the distance from the lightoutput opening 2104 to the light input opening 2102 may be considered tobe the height of the reflector 2110 and the planes 14A, 14B, 14E, and14F may be considered to each have an axis extending along the heightaxis of the reflector 2110. In addition, the pairs of midplanes 14A and14B, and 14E and 14F, are orthogonal to one another. Preferably, as seemin the midplanes 14A, 14B, 14E, and 14F, the interior sidewalls 2112 a,2112 b, 2112 c, 2112 d each follow a CPC profile and have the curvatureof a compound parabolic concentrator.

The optical system comprising the reflectors and lens providesexceptional spatially uniform light output. FIGS. 15A and 15B illustrateexamples of uniformity maps for the light output of the reflectors ofFIGS. 14A-14C and 14D-14F, respectively. In these maps, different colorsindicate different light intensity. Advantageously, as illustrated, thecolors and intensities are highly uniform, indicating high spatialuniformity.

The light output also has good angular uniformity. FIG. 16 illustratesan example of a map showing the intensity of light output, in anglespace, for the reflector of FIGS. 14A-14C in conjunction with a lensaccording to embodiments herein. V corresponds to the angular spread oflight output along the major (longer) axis of the light output opening2104 (FIG. 14A), H corresponds to the angular spread of light outputalong the minor (short) axis of the light output opening 2104, andDiagonal corresponds to the angular spread of light output along thediagonal of the light output opening. Notably, the cutoff for each of V,H, and Diagonal is sharp, indicating that the angles at which lightexits the lens are similar, with minimal stray light outside of thoseangles.

In some embodiments, the reflector and lens system may form part of anarray of reflectors and lens. Because the reflector may simply be formedin an appropriately shaped volume, an array of reflectors may be formedin a single body of material. FIGS. 17A-17B illustrates perspectiveviews of examples of arrays of the reflectors of FIGS. 14A-14C and14D-14F, respectively. FIG. 17A shows reflectors having elliptical lightoutput openings, and FIG. 17B shows reflectors having elongated outputopenings with straight and curved sides, as discussed with respect toFIGS. 14D-14F. In both FIGS. 17A and 17B, a plurality of the reflectors2110 may be formed in a body of material 2200, e.g., a plate ofmaterial. While shown as being similar for ease of illustration, it willbe appreciated that the sizes and/or shapes of the reflectors in thebody 2200 may vary in some embodiments.

It will be appreciated that the body 2200 may be formed of variousmaterials that have sufficient mechanical integrity to maintain thedesired shape of the reflectors 2110. Examples of suitable materialsinclude metals, plastics, and glasses. As discussed herein, the body2200 may be a plate. In some embodiments, body 2200 is a continuous,unitary piece of material. In some other embodiments, the body 2200 maybe formed by joining together two or more pieces of material.

The reflectors 2110 may be formed in the body 2200 by various methods.For example, the reflectors 2110 may be formed by machining the body2200, or otherwise removing material to carve out the reflectors 2110.In some other embodiments, the reflectors 2110 may be formed as the body2200 is formed. For example, the reflectors 2110 may be molded into thebody 2200 as the body 2200 is molded into its desired shape. In someother embodiments, the reflectors 2110 may be formed by rearrangement ofmaterial after formation of the body 2200. For example, the reflectors2110 may be formed by imprinting.

Once the contours of the reflectors 2110, the reflector volumes mayundergo further processing to form inner surface having the desireddegree of reflection. In some embodiments, the surface of the body 2200may itself be reflective, e.g., where the body is formed of a reflectivemetal. In such cases, the further processing may simply includesmoothing the interior surfaces of the reflectors 2110 to increase theirreflectivity. In some other embodiments, the interior surfaces of thereflectors 2110 may be lined with a reflective coating.

will be appreciated that shaping the reflector 2110 as discussed aboveallows the light output of the reflector to be shaped in angle space andprovides an asymmetrical angular distribution. Advantageously, thereflector shape may be used to provide light output that matches thedesired display aspect ratio, as noted herein. In some otherembodiments, the desired aspect ratio may be achieved using a maskplaced forward of the lens.

FIG. 18 illustrates a perspective view of an example of an opticalsystem having arrays of light emitters 2140, reflectors 2110, and lens2120, and a mask 2400. In some embodiments, the light emitters 2140 aremounted on a supporting substrate 2300, e.g., a printed circuit board.The spatial layout of the light emitters 2140 and the reflectors 2110are preferably matched, such that each light emitter 2140 is verticallyaligned with an individual corresponding reflector 2110. In someembodiments, the arrays of light emitters 2140, reflectors 2110, andlens 2120, and optionally the mask 2400 may form the light module 540(FIG. 6 ).

In some embodiments, the light emitters 2140 may all be similar. In someother embodiments, at least some of the light emitters 2140 may bedifferent, e.g., some light emitters may output light of a differentwavelength or range of wavelengths from other light emitters. Forexample, the light emitters 2140 may form groups of light emitters,e.g., three groups of light emitters, with each group emitting light ofwavelengths corresponding to a different color (e.g., red, green, andblue). In some embodiments, more than three groups of light emitters(for emitting light of more than three different ranges of wavelengths)may be present. The different groups of light emitters may be utilizedto provide light of different component colors for a display system,such as the display system 250 (FIG. 6 ). For example, light emitters ofeach group may be utilized to emit the light rays 770, 780, 790 (FIGS.9A-9B).

In some embodiments, the light emitters, reflectors, and lens areutilized to provide light to the stack of waveguides 660 (FIGS. 9A-9C).In such embodiments, in addition to a match between the spatial layoutof the light emitters 2140 and the spatial layout of the reflectors2110, the light emitters 2140 and the reflectors 2110 are preferablyalso arranged to match the spatial layout of incoupling optical elements(e.g., incoupling optical elements 700, 710, 720) in the stack ofwaveguides 660. Preferably, the spatial layout of the light emitters2140 and reflectors 2110 match the spatial layout of the incouplingoptical elements 700, 710, 720 such that the spatial arrangement of thereflectors 2110, as seen in a plan view, corresponds one-to-one with aspatial arrangement of the light incoupling optical elements 700, 710,720. With such an arrangement, light from a particular light emitter maybe reliably directed into an associated one of the waveguides 670, 680,690, without being directed into others of the waveguides 670, 680, 690.

With continued reference to FIG. 18 , with the optical system 2100oriented as illustrated, the light input opening of the reflector is ata bottom of the body 2200, and the light output opening is at the top ofthe body 2200. Preferably, the lower surface of the body 2200 iscontoured to lay flat on the upper surface of the substrate 2300, suchthat light does not significantly propagate into a reflector 2110 fromlight emitters other than the reflectors matching light emitter.Advantageously, both the lower surface of the body 2200 and the suppersurface of the substrate 2300 may be flat, which facilitates a tight fitat the interface between the body 220 and the substrate 2300, which mayprevent undesired stray light from reaching individual reflectors 2110.

Lenses 2120 are provided at the light output openings of the reflectors2110. As illustrated, each reflector 2110 has an individual associatedlens 2120. In some other embodiments, some or all of the lenses may beformed in a single sheet of material. In such embodiments, the sheet ofmaterial is preferably thin, e.g., sufficiently thin to minimize lightleakage between reflectors, while maintaining sufficient structuralintegrity to hold the lenses together.

With continued reference to FIG. 18 , the mask 2400 is provided forwardof the lenses 2120. The mask 2400 has openings 2402, e.g., cutouts, inthe desired shape for the light output. Thus, the mask 2400 may beutilized for spatial light shaping. Openings 2402 preferably have asmaller area than the light output openings of the reflectors. In someembodiments, the mask surface facing into the reflector (e.g., thebottom surface of the mask 2400) is reflective, which may increase theefficiency and brightness of the light module comprising the lightemitter 2140, reflector 2110, and lens 2120. In some other embodiments,the bottom surface is absorptive, which, by preventing randomreflections between the bottom surface of the mask and the reflector2110, may provide a higher degree of control over the paths of lightpassing through the openings 2402 from the reflector 2110.

In addition to defining the contours of the reflectors 2110, the body2200 may include other structures for other purposes. FIG. 19illustrates a perspective view of an example of the body 2200 having anarray of reflectors 2110 and indentations 2210 for light emitterstructures such as wiring. The indentations 2210 are shaped and have adepth such that they can accommodate portions of a light emitter 2140(FIG. 18 ) or structures connected to the light emitter 2140, so thatthe body 2200 may fit tightly against the substrate 2300 without lightleakage. As with the reflectors 2110, the indentations 2210 may beformed by various methods, include machining, molding, and imprinting.

In some embodiments, the body 2200 may have a uniform thickness. In someother embodiments, the thickness of the body 2200 may vary. FIGS.20A-20B illustrate perspective views of examples of the body 2200 ofmaterial having reflectors with different heights. Because thereflectors extend completely through the body 2200, different heightsfor the reflectors may be achieved by setting the thickness of the body2200 at different heights. As an example, FIGS. 20A-20B illustrate threeheights or levels 2200 a, 2200 b, and 2200 c. It will be appreciatedthat fewer or more levels may be provided as desired, and the levels maybe arranged differently from that illustrated in some embodiments.

The different heights for the reflectors 2110 may provide advantages inapplications in which different groups of light emitters 2140 (FIG. 18 )emit light of different wavelengths. Light of different wavelengths mayfocus at different distances from the corresponding light emitter 2140.As a result, reflectors 2110 with different heights that are selectedbased on the distance that the light is best focused may be expected toprovide improvements in image quality where the light emitters 2140,reflectors 2110, and lenses 2120 are used in a display system. In someembodiments, where the lens 2120 is positioned one focal length from theassociated light emitter 2140, the distance corresponding to one focallength may vary with the wavelength of the emitted light, and thethickness of the part of the body 2200 accommodating that light emitter2140 and the associated reflector 2110 and lens 2120 may be selected toallow placement of the lens 2120 at the appropriate one focal lengthdistance from the light emitter 2140.

In some other embodiments, the reflectors 2110 may all have the sameheight and the lens 2120 for different groups of light emitters 2140 maybe different. For example, the lens 2120 for different groups of lightemitters 2140 may be configured to have different focal lengths, toaccount for differences caused by light of different wavelengths.

With reference now to FIGS. 21A-21E, various views of an example of areflector 2110 are illustrated. It will be appreciated that thereflector 2110 may assume various shapes that follow a CPC profile. Insome embodiments, the reflector 2110 may be formed by a plurality ofsides, or facets, each of which has a CPC profile as seen in a sideview; that is, in some embodiments, all interior sides of the reflector2110 may have a CPC profile, when each side is seen in a side view. Theview of FIG. 21A shows the reflector 2110 as seen looking down on thereflector from the light input opening end of the reflector. The viewsof FIGS. 21 B and 21C show the reflector 2110 as seen from opposingsides. The view of FIG. 21D shows the reflector 2110 as seen from a sideorthogonal to the sides seen in views B and C. The view of FIG. 21Eshows a perspective view of the reflector 2110 as viewed from the lightoutput end of the reflector. The sidewalls 2112A and 2112B may both haveCPC profiles, and the sidewalls 2112C and 2112D may also both have CPCprofiles. In addition, all other sides may have a CPC profile as seen inside views. In addition, in some embodiments, as can be seen in theviews of FIGS. 21A and 21E, each side of the reflector 2110 is linear orflat, when viewed in a cross-sectional view taken along a planetransverse to the height axis (extending from an input end 2102 to anoutput end 2104) of the reflector 2110.

In some embodiments, two opposing sides, e.g., sides 2112 C and 2112 Dor sides 2112 a and 2112 b have the same CPC profile, but that profilediffers from the CPC profile of all other sides. In addition, all theother sites may have the same CPC profile. Thus, in some embodiments thecurvature of all interior sides of the reflector 2110 may be the sameexcept for that of a pair of opposing interior sides. In some otherembodiments, as noted herein, the interior sides of the reflector 2110may follow other contours, including that of an ellipse, hyperbola, orbiconic shape, or may be substantially linear from an input end 2102 toan output end 2104 of the reflector 2110.

Preferably, the total number sides is an even number, for example 4, 6,8, 10, 12, etc. In some embodiments, the total number of sides may be 8or greater, which has been found to provide exceptionally spatiallyuniform light output.

It will be appreciated that the light input opening 2102 may be sized toaccommodate the underlying light emitter. In some embodiments, the lightemitter may have a maximum width of about 500 μm or greater, 600 μm orgreater, 700 μm or greater, or 800 μm or greater. In some embodiments,the light input opening 2102 may have a maximum width of 500 μm orgreater, 600 μm or greater, 700 μm or greater, 800 μm or greater, 900 μmor greater, or 1 mm or greater. In some embodiments, the light inputopening 2102 has a width that is less than 2 mm, less than 1.5 mm, orless than 1 mm.

FIGS. 22A-22B illustrate additional perspective views of the reflector2110 of FIG. 21 . FIGS. 22C-22D illustrate yet other additionalperspective views of the reflector of FIG. 21 as seen from the lightoutput opening side and the light input opening side, respectively, ofthe reflector 2110.

FIGS. 23A and 23B illustrate examples of uniformity maps for the lightoutput of a reflector having a rounded profile (as seen incross-sections taken along a plane transverse to the height axis of thereflector) and a reflector having sharp corners at the intersections ofsubstantially linear interior sidewalls (as seen in cross-sections takenalong a plane transverse to the height axis of the reflector),respectively. Undesirably, as shown in FIG. 23A, the rounded profilereflector provides light output having an area of low intensity in themiddle of the map. While this low intensity area is undesirable initself, it will be appreciated that the middle of the map may also bethe center of the viewer's field of view, and the viewer may haveespecially high sensitivity to nonuniformities in this area.Advantageously, as shown in FIG. 23B, an 8-sided reflector having sharpcorners and CPC profiles for each side, as discussed above regardingFIGS. 21-22D, provides highly uniform light output.

Various example embodiments of the invention are described herein.Reference is made to these examples in a non-limiting sense. They areprovided to illustrate more broadly applicable aspects of the invention.Various changes may be made to the invention described and equivalentsmay be substituted without departing from the spirit and scope of theinvention.

For example, while advantageously utilized with AR displays that provideimages across multiple depth planes, the augmented reality contentdisclosed herein may also be displayed by systems that provide images ona single depth plane.

In addition, while advantageously applied as a light source for displaysystems, the reflector and lens system disclosed herein may be utilizedin other applications where high spatially uniform light is desired.Moreover, while the simply mechanical construction of the reflector andlens facilitates their use in arrays of reflectors and lens, thereflectors and systems may also be used in an optical system with asingle reflector and associated lens.

It will also be appreciated that, while the reflector 2110 (FIG. 14 C)may have a notch 2114 to accommodate connectors such as wire bonds for alight emitter, in some other embodiments, the notch 2014 may beeliminated. For example, the sidewall 2112 c may continue to the samelevel as other sidewalls of the reflector 2110. In such embodiments, alight emitter that does not have a protruding wire bond may be utilized,and the sidewalls of the reflector 2110 may extend to contact asubstrate, such as a printed circuit board, supporting the lightemitter. An example of a light emitter without a protruding wire bond isa flip chip LED. It has been found that the wire bond extending over thelight emitter may cause a shadow that produces visible artifacts inimages formed using the light emitter. Advantageously, eliminating thewire bond and extending the reflector sidewalls to the light emittersubstrate may eliminate such artifacts and improve image quality.

In addition, many modifications may be made to adapt a particularsituation, material, composition of matter, process, process act(s) orstep(s) to the objective(s), spirit or scope of the present invention.Further, as will be appreciated by those with skill in the art that eachof the individual variations described and illustrated herein hasdiscrete components and features which may be readily separated from orcombined with the features of any of the other several embodimentswithout departing from the scope or spirit of the present inventions.All such modifications are intended to be within the scope of claimsassociated with this disclosure.

The invention includes methods that may be performed using the subjectdevices. The methods may comprise the act of providing such a suitabledevice. Such provision may be performed by the user. In other words, the“providing” act merely requires the user obtain, access, approach,position, set-up, activate, power-up or otherwise act to provide therequisite device in the subject method. Methods recited herein may becarried out in any order of the recited events that is logicallypossible, as well as in the recited order of events.

Example aspects of the invention, together with details regardingmaterial selection and manufacture have been set forth above. As forother details of the present invention, these may be appreciated inconnection with the above-referenced patents and publications as well asgenerally known or appreciated by those with skill in the art. The samemay hold true with respect to method-based aspects of the invention interms of additional acts as commonly or logically employed.

In addition, though the invention has been described in reference toseveral examples optionally incorporating various features, theinvention is not to be limited to that which is described or indicatedas contemplated with respect to each variation of the invention. Variouschanges may be made to the invention described and equivalents (whetherrecited herein or not included for the sake of some brevity) may besubstituted without departing from the spirit and scope of theinvention. In addition, where a range of values is provided, it isunderstood that every intervening value, between the upper and lowerlimit of that range and any other stated or intervening value in thatstated range, is encompassed within the invention.

Also, it is contemplated that any optional feature of the inventivevariations described may be set forth and claimed independently, or incombination with any one or more of the features described herein.Reference to a singular item, includes the possibility that there areplural of the same items present. More specifically, as used herein andin claims associated hereto, the singular forms “a,” “an,” “said,” and“the” include plural referents unless the specifically stated otherwise.In other words, use of the articles allow for “at least one” of thesubject item in the description above as well as claims associated withthis disclosure. It is further noted that such claims may be drafted toexclude any optional element. As such, this statement is intended toserve as antecedent basis for use of such exclusive terminology as“solely,” “only” and the like in connection with the recitation of claimelements, or use of a “negative” limitation.

Without the use of such exclusive terminology, the term “comprising” inclaims associated with this disclosure shall allow for the inclusion ofany additional element—irrespective of whether a given number ofelements are enumerated in such claims, or the addition of a featurecould be regarded as transforming the nature of an element set forth insuch claims. Except as specifically defined herein, all technical andscientific terms used herein are to be given as broad a commonlyunderstood meaning as possible while maintaining claim validity.

The breadth of the present invention is not to be limited to theexamples provided and/or the subject specification, but rather only bythe scope of claim language associated with this disclosure.

1-20. (canceled)
 21. A head-mounted display system comprising: areflector comprising: an input end; an output end; an even number offaceted sides extending between the input end and the output end,wherein two opposing sides of the reflector define a first curvedcross-sectional profile and two other opposing sides of the reflectordefine a second curved cross-sectional profile different from the firstcross-sectional profile; a lens located one focal length of the lensaway from the input end of the reflector; a light modulating deviceconfigured to receive and to modulate light outputted from the lens toform image light; and a stack of waveguides, wherein each waveguide ofthe stack comprises: a light incoupling optical element configured toincouple image light received from the light modulating device; and alight outcoupling optical element, wherein light incoupling opticalelements of different waveguides, as seen in a top-down plan view, arelaterally offset from one another.
 22. The head-mounted display systemof claim 21, wherein the reflector is one of an array of reflectors. 23.The head-mounted display system of claim 22, further comprising aplurality of light emitters, wherein each of the array of reflectors hasan associated one of the plurality of light emitters disposed at aninput end of the each of the reflectors.
 24. The head-mounted displaysystem of claim 23, wherein some of the plurality of light emitters areconfigured to emit light of different wavelengths than others of theplurality of light emitters.
 25. The head-mounted display system ofclaim 21, wherein the lens is disposed at the output end of thereflector, wherein the reflector extends one focal length of thereflector.
 26. The head-mounted display system of claim 21, wherein thefirst cross-sectional profile is a first compound parabolic concentrator(CPC) profile.
 27. The head-mounted display system of claim 26, whereinthe second cross-sectional profile is a second compound parabolicconcentrator (CPC) profile, wherein the first and the second CPCprofiles are different.
 28. The head-mounted display system of claim 21,wherein the light modulating device comprises a spatial light modulator.29. The head-mounted display system of claim 28, wherein the spatiallight modulator comprises a liquid crystal display (LCD).
 30. Thehead-mounted display system of claim 29, wherein the liquid crystaldisplay is a liquid crystal on silicon (LCoS) display.
 31. Thehead-mounted display system of claim 21, further comprising a maskbetween the reflector and the spatial light modulator, wherein the maskhas an opening smaller than the output end.
 32. The head-mounted displaysystem of claim 21, wherein the mask is between the lens and the spatiallight modulator.
 33. The head-mounted display system of claim 21,wherein the mask has a mask surface facing the reflector, wherein themask surface is absorptive.
 34. The head-mounted display system of claim21, wherein a cross-sectional shape of the input end is different from across-sectional shape of the output end.
 35. The head-mounted displaysystem of claim 21, wherein the light emitters are light emittingdiodes.
 36. The head-mounted display system of claim 21, wherein thereflector is one of a plurality of reflectors formed by sidewalls ofopenings extending through a thickness of a common unitary body, whereineach reflector has an associated lens forward of the output opening ofthe reflector.
 37. The head-mounted display system of claim 36, whereinthe unitary body has a multi-tiered surface, wherein some reflectorshave output openings on a different tier than other reflectors.
 38. Thedisplay system of claim 37, wherein each reflector has an associatedlight emitter, wherein some light emitters are configured to emit lightof different wavelengths than other light emitters, wherein a height ofthe tiers varies with a wavelength of light emitted by an associatedlight emitter.